It has become increasingly clear that bacterial adherence to mucosal surfaces is an important determinant of pathogenesis. The role of this phenomenon in gastro-intestinal, genitourinary and oral disease is being intensely investigated. Our studies are directed towards elucidating whether this phenomenon occurs in the pathogenesis of respiratory tract disease and if so, what is its significance. We also wish to study host and bacterial factors involved in adherence to this area of the body. The intact respiratory system is remarkably resistant to infection but becomes susceptible after a variety of insults. We therefore propose to study bacterial adherence to the tracheobronchial tree after several different insults. We propose to study this phenomenon after viral infections, mechanical trauma, chemical damage, and cytotoxic chemotherapy, all of which are conditions under which pneumonias occur. After the conditions which predispose to adherence have been defined and the organism which is capable of adhering has been identified, we propose to test whether adherence can be inhibited by chemicals or by the immune system.